With the progress of time and the development of science and technology, from illuminating with flame to fluorescent illumination, the characters of the illuminations that people required continues rising. However, problems such as worsening environment and shortages of energy are brought out with the rapid and continues development of economy. Therefore, it is a hot research issue that a new light source having advantages of high-efficient, environmental safe, long lifetime, energy-saving is developed to replace traditional light source by each nations. Novel field emission light source which is also called cold cathode light source, having the virtues of environmental safe, energy-saving, light, et al, may be widely applied in various lighting fields, and has great potential. It has important realistic significance in response to national strategy of carbon reducing and energy saving.
Development of field electron emission in cold cathode went through three courses which are Micro-tip, wide band-gap film, and quasi one-dimension nanomaterial in succession. Emission stability of micro-tip cold cathode is not good because the turn-on field is high, mechanical performance, chemical and physical properties are unstable, such as it is easily oxidized, and damaged by ion bombardment. Short lifetime and high manufacture cost restrict the application of this type cold cathode in vacuum electron source device. The people discovered new wide band-gap film cold cathode material had excellent field emission property. It substantially includes diamond and film interrelated. They have the virtues of low surface electron affinities, high heat conductivity, stable chemical and physical properties, unique ultra-high hardness, and easily achieve preparation in large area, and these favor the application in field electron emission display. However, shortcomings of film cold cathode that it is difficult to prepare evenly in large area, and the turn-on electric field is high, restrict the application process.
It should be understood from the foregoing that it is difficult to commercially apply any one of the micro-tip matrix cold cathode or the film cold cathode widely. Quasi one-dimension nanomaterial, which develop simultaneously with the film cold cathode, became research hot point in field electron emission field because of their unique geometry, stable chemical and physical properties and excellent field electron emission property, and it is a breakthrough of the commercially application of the big size field electron emission device. Carbon nanotubes as a typical Quasi one-dimension structure, have 103˜104 times electric field enhancement while applied in cold cathode of field electron emission device and tips of carbon nanotubes. According to research, carbon nanotubes have stable chemical and physical properties, excellent electric current field emission property, and capability to endure super large emission electric current density. Because the growing temperature of the carbon nanotubes is higher than softening temperature, the carbon nanotubes may be only grown on heat-resistant substrate, and the manufacture cost is high, it is difficult to grow carbon nanotubes in large area on glass directly. So, people prepared carbon nanotubes firstly, then the carbon nanotubes are printed on the glass substrate by screen printing to make the applications of the carbon nanotubes popularized. The carbon nanotubes printed on the glass substrate are easily to detach from the substrate, and emission is uneven and unstable. People selected metal particulates and oxide particulates as filler to solve the problem of adhesion between the carbon nanotubes and the substrate, and uneven emission. At present, it could solve problem of adhesion between the carbon nanotubes and the substrate at same level, however it is difficult to solve the problems of uneven and unstable emission. This is due to electricity conductive properties of carbon nanotubes and emission properties of field electrons are different due to the different geometric structures (height, diameter and chirality), and it is adverse to the application of the carbon nanotubes in the vacuum micro-electron device. According to prior art, it is difficult to prepare carbon nanotubes in large area which have uniform heights, diameters, and chiralities.